Cancer is one of the major causes of human morbidity and mortality. Cancer treatment is challenging because it is difficult to kill cancer cells without damaging or killing normal cells. Damaging or killing normal cells during cancer treatment causes adverse side effects in patients and can limit the amount of anticancer drug administered to a cancer patient. It is also difficult to kill cancer cells in hypoxic regions distant from the vasculature where anticancer drugs fail to penetrate.
Many cancer cells are more hypoxic relative to normal cells. Tumor hypoxia is associated with resistance to anticancer therapies, cancer relapse, and poor prognosis. Certain drugs in preclinical and clinical development target hypoxic cancer cells. These drugs, called hypoxia-activated prodrugs or “HAPs” are administered in an inactive, or prodrug, form but are activated, and become toxic, in a hypoxic environment. US 2010/0137254 and US 2010/0183742, each of which is incorporated herein by reference, describe HAPs such as those having a structure defined by formula (I), below:
where Z3 is selected from the group consisting of:
andX4 is Cl or Br.
The compounds known as TH-302 and TH-281 are particularly promising therapeutic candidates. TH-302 (see Duan et al., 2008, J. Med. Chem. 51: 2412-2420, incorporated herein by reference), known by the chemical name (2-bromoethyl)({[(2-bromoethyl)amino][(2-nitro-3-methylimidazol-4-yl)methoxy]phosphoryl})amine, has the structure represented below:

Another promising HAP is TH-281, which differs from TH-302 only in that it has 2-chloroethyl groups instead of the 2-bromoethyl groups present in TH-302.
The aforementioned HAPs can be used in combination with other drugs, for the treatment of pancreatic cancer or any other cancer, such as gemcitabine, gemcitabine in combination with nab-paclitaxel (Abraxane), or FOLFIRINOX based on folinic acid (Leucovorin), fluorouracil (5-FU), irinotecan (Camptosar) and oxaliplatin (Eloxatin) (see e.g., WO 2013/126539, PCT/US2014/047885, and Conroy et al., 2013, Current Oncology Reports 15(2): 182-189; each incorporated herein by reference).
However, while nearly all tumors contain hypoxic regions, there is a wide variability among patients in how hypoxic a tumor of a given cancer type may be. For example, using median tumor pO2 (mm Hg) as a measure of tumor hypoxia, one study of 33 soft tissue sarcoma patients showed that the median tumor pO2 ranged from about 1 to about 70 mm Hg (see Nordsmark et al., 2001, Brit. J. Cancer 84(8): 1070-1075). Another study of 58 head and neck cancer patients showed the hypoxic fraction ranged from just above 90% to 1%. Thus, if greater tumor hypoxia correlates with a better response to HAP-mediated anti-cancer therapy, then this variability in tumor hypoxia will translate into a variable response to HAP anti-cancer therapy.
Enolase enzymes are encoded by three genes (ENO1, ENO2 and ENO3) and can produce multiple forms of enolase enzymes, including α-enolase (ENO1), γ-enolase (ENO2) and β-enolase (ENO3) (Capello et al., 2011, FEBS J. 278: 1064-1074; incorporated herein by reference). Enolase enzymes are glycolytic enzymes that catalyze the conversion of 2-phosphoglycerate to phosphoenolpyruvate. They can also localize to cytoplasmic membrane, acting as receptors for plasminogen and be secreted into the blood where serum levels can be measured. A serum-based immunoassay for ENO2 (NSE) is used in the diagnosis of small cell lung cancer, and other neural crest derived tumors and multiple immunoassay formats are available to measure ENO2 (Kasprzak et al., 2007, Pol J Pathol. 58: 23-33, incorporated herein by reference). US 2004/0219572 is directed to markers for the diagnosis of pancreatic cancer, including alpha-enolase, which is incorporated herein by reference. ENO1 and ENO2 are hypoxia-induced genes and the glycolytic activity of the encoded enzymes is thought to play a role in the altered cellular metabolism and survival of hypoxic cancer cells. Hypoxia results in a number of biological responses mediated by hypoxia signal transduction pathways. Two of the primary hypoxia signal transduction pathways are the HIF (hypoxia inducible factor) pathway and the UPR (unfolded protein response) pathway. The HIF-1 transcription factor, the master control factor for the hypoxic response in cells, is believed to regulate the expression of ENO1 and ENO2 since both genes contain HIF-1 transcription factor binding sites in their promoter regions (Tanimoto et al., 2010, HUGO J 4:35-48). Further enolase-related matter is described in US 2007/0077583, US 2010/0028907, US 2012/0164146 and Diaz-Ramos et al., 2012, J Biomed Biotech 2012: 1-12), each of which is incorporated herein by reference.
There remains a need for new methods of determining whether a cancer patient is likely to respond favorably to treatment with hypoxia-activated achiral phosphoramide mustards, such as TH-302, and/or to treat such patients. The present invention meets these needs.